1. Field of the Invention
This invention relates to optical waveguide connectors for coupling waveguides and/or optical fibers and to methods of making the connectors.
2. Description of Related Art
In optical communication systems, messages are transmitted typically through optical fibers by carrier waves of optical frequencies that are generated by sources, such as lasers or light emitting diodes. There is much current interest in such optical communication systems because they offer several advantages over other communication systems, such as having a greatly increased number of channels of communication and the ability to use other materials besides expensive copper cables for transmitting messages.
One such means for conducting or guiding waves of optical frequencies from one point to another is called an optical waveguide. The operation of an optical waveguide is based on the fact that when a medium which is transparent to light is surrounded or otherwise bounded by another medium having a lower or higher refractive index, light introduced along the inner medium's axis is highly reflected at the boundary with the surrounding medium, thus, producing a guiding effect.
The most frequently used material for such a waveguide device is glass, which is formed into a fiber of specified dimensions. As the development of optical circuits proceeded, it became necessary to have devices which could couple one optical fiber to another.
A traditional way for making a connection between ends of two optical fiber cables is as follows. First, a protective jacket is removed from several inches of each of the optical fiber cables near ends to be joined. When the jacket is removed, the remainder comprises a core surrounded by cladding which together have an outer diameter of about 125 microns (.mu.m) which is about 3 times the diameter of a human hair. Second, the thin fragile remainder is threaded by hand through a separate ferrule which can be either glued onto the optical fiber with, for instance, epoxy or fixed to the optical fiber by crimping, i.e., squeezing and deforming, a portion of the ferrule firmly around the optical fiber. Traditionally, ferrules were epoxied onto the fibers. More recently, the industry is inclined to crimp ferrules on fibers because it takes significantly less time, i.e., one does not have to wait for the epoxy to dry. Third, the optical fiber extending beyond the end of each of the ferrules is cleaved, which entails scoring and breaking the optical fiber, less than one diameter or 125 .mu.m beyond the end of the ferrule. Fourth, the ends of the optical fibers are encapsulated in epoxy and then polished, typically, first with a coarse, e.g., 8 .mu.m, grit paper until the ends extend about 20 to 25 .mu.m beyond the end of the corresponding ferrules and then with one or more finer, e.g., 1 .mu.m and/or 0.3 .mu.m, grit papers until the ends of the optical fibers are flush with the end of their corresponding ferrules. Due to the size of the optical fibers, this polishing requires the skill of an experienced individual to make an acceptable end. Finally, the ferrules are manually inserted into a connector housing assembly which is intended to position the optical fibers such that they are adjacent to one another with their optical axes in alignment with respect to each other. This is a time consuming process which requires skill and, as a result, is costly.
Some optical fibers are interconnected by other optical fibers cut to length. Other optical fibers are interconnected by optical waveguide devices made from materials other than glass.
One method used to form an optical coupling device made from materials other than glass involves the application of standard photolithographic processes and diffusion. See U.S. Pat. No. 4,609,252. However, such methods are relatively time consuming, costly and wet, thereby, messy.
Photohardened films containing a waveguide have been proposed to interconnect one optical fiber to another optical fiber. For example devices, see U.S. Pat. Nos. 3,689,264, 4,609,252, 4,637,681, 4,883,743, and 5,125,054.
However, regardless of how the fibers were connected, connecting optical fibers to one another or to optical waveguide devices has traditionally been a problem. Most connections need to be made by hand. In view of the small dimensions of the fibers, alignment problems exist in most, if not all, connection methods. Because of the alignment problems, most connections are permanent, rather than detachable. Most methods for connecting optical fibers with other fibers, or other types of waveguides, are time consuming processes and costly. When connections are needed between a first plurality of optical waveguides and a second plurality of optical waveguides, the process only becomes more difficult.